1. Field of the Invention
The present invention relates to a device for wireless data transmission from a source to a sink, using ferrite rod and elongate frame antennae during the track-bound passage of a response device arranged at the source end and an interrogation device arranged at the sink end, wherein the interrogation device contains a transmitter which serves to transfer the energy for the transmission of an item of data to a receiver contained in the response device.
2. Description of the Prior Art
In order that items of data may be transferred in punctiform fashion from passive response devices to active interrogation devices between objects moving on tracks and link devices, devices of the type referred to above have been developed ("Automatisches Lesen von Kennungen fur Guterwagen", Siemens Magazine, 37th Edition Vol. 11, November 1973, pp. 779-785). In devices of this type, the actual data transmission takes place by way of a plurality of ferrite rod antennae which are arranged transversely to the track direction, whereas the energy transfer takes place via frame antenna.
In the event that the antenna arrangement is to be relatively narrow in the track direction, a configuration of this type is not suitable.
For these circumstances, an apparent idea would be to arrange the ferrite rode antennae provided for the data transmission in the track direction. As a result, the energy transfer and the data transfer would still be decoupled from one another by a difference of 90.degree. in the polarization direction of the corresponding electrical signals, but such an arrangement would have the disadvantage that on passing ferrite rod antennae of the response device and of the interrogation device arranged in the track direction, the signal which serves for data transmission would be input coupled into the receiving ferrite rod antenna with a phase position which changes twice by 180.degree.. It would require a high technological expense to analyze such a signal.